audio: copier: validate channels_count in copier_set_gain

channels is host-controlled (8-bit, 0-255).
Without validation it drives the memcpy length (channels * sizeof(uint16_t))
against a MAX_GAIN_COEFFS_CNT-sized stack buffer and, for channels == 0,
causes divide-by-zero in the coefficient replication loop.
Reject values outside [1, MAX_GAIN_COEFFS_CNT].

Signed-off-by: Adrian Bonislawski <adrian.bonislawski@intel.com>

Author: abonislawski

src/audio/copier/copier_gain.c

@@ -172,6 +172,11 @@ int copier_set_gain(struct comp_dev *dev, struct copier_gain_params *gain_params
 		return -EINVAL;
 	}
 
+	if (channels <= 0 || channels > MAX_GAIN_COEFFS_CNT) {
+		comp_err(dev, "invalid channels count %d", channels);
+		return -EINVAL;
+	}
+
 	/* Set gain coefficients */
 	comp_info(dev, "Update gain coefficients from DMA_CONTROL ipc");